• Tribology and Lubricants
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• v.34 no.1
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• pp.9-15
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• 2018

Modern high-performance automotive turbochargers (TCs) implement ceramic hybrid angular contact ball bearings in series with squeeze film dampers (SFDs) to enhance transient responses, thereby reducing the overall emission levels. The current study predicts the rotordynamic responses of the commercial automotive TCs (compressor wheel diameter = ~53 mm, turbine wheel diameter = ~43 mm, and shaft diameter at the bearing locations = ~7 mm) supported on ball bearings and SFDs for various design parameters of SFDs, including radial clearance, axial length, lubricant viscosity, and rotor imbalance conditions (i.e., amplitudes and phase angles) while increasing rotor speed up to 150 krpm. This study validates the predictive rotor finite element model against measurements of mass, polar and transverse moments of inertia, and free-free mode natural frequencies and mode shapes. A nonlinear rotordynamic model integrates nonlinear force coefficients of SFDs to calculate the transient responses of the TC rotor-bearing system. The predicted results show that SFD radial clearances, as well as phase angles of rotor imbalances, have the paramount effect on the dynamic responses of TC shaft motions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.3-20
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• 1995

Advanced ceramics have excellent thermal resistance, wear resistance, corrosion resistance, and other properties, and are promising materials as structural materials. Over the past decade, they have been applied to some machine parts, for example, glow plugs and turbochargers of automotive engines. In the case where the advanced ceramics are used as these structural parts, te low-dimensional accuracy of sintered bodies requires secondary machining.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.851-856
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• 2012

Automotive turbochargers have become common in gasoline engines as well as diesel engines. They are excellent devices to effectively increase fuel efficiency and power of the engines, but they unfortunately cause several noise problems. The noises are classified into mechanical noises induced from movement of a rotating shaft and aerodynamic noises by air flow in turbochargers. The mechanical noises are whine and howling noises, and the aerodynamic noises are BPF (blade-passing frequency), pulsation, surge, some special frequency noises. These noises are bothering passengers because their levels are higher or their frequencies are clearly separated from engine or vehicle noises. The noise investigated in this paper is a BPF noise induced by compressor wheels, whose frequency is the multiplication of the number of compressor wheel blades and its rotational speed. The noise is strongly dependent upon the geometry of wheels and the number of blades. This study tried to apply a groove close to the inlet side of compressor wheels in order to reduce the BPF noise. The groove has successfully reduced the noise of narrow band frequency of a turbocharger. It shows that the groove could reduce the wide band frequency noise, the compressor BPF noise with a best shape of the groove.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.686-686
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• 2013

Automotive turbochargers have become common in gasoline engines as well as diesel engines. They are excellent devices to effectively increase fuel efficiency and power of the engines, but they unfortunately cause several noise problems. The noises are classified into mechanical noises induced from movement of a rotating shaft and aerodynamic noises by air flow in turbochargers. In addition to, there is a mechanical noise caused from movement of an actuator, electronically controlling a wastegate valve. It is called as valve rattle noise. The actuator is connected to a valve through a linkage. The noise occurs only if the valve is open, where the linkage is freely contact to neighbor structures without being constrained by any external forces. This condition allows impacts by the pulsation of exhaust gas, and the vibration from the impacts spreads out through turbine housing, causing the rattle noise. The noise is not in mechanical operating wastegate turbochargers because the linkage of an actuator is strongly connected by actuating force. For the electronic wastegate turbocharger, this paper proposed a test device to show the noise generating mechanism with a small vibration motor having an unbalanced shaft. It also shows how to reduce the noise - reduction of linkage clearances, inserting wave washers into a connection, and applying loose fitting in bushing embracing a valve lever to turbine housing.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.5
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• pp.46-59
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• 1990

The development of the effective computer simulation program which predicts the performances and emissions of the multi-cylinder turbocharged gasoline engine has been described in the first paper. In this paper, the comparison between the predictions and experiments of the transient pressure at each point in the intake and exhaust systems was made to examine the validity and availability of the simulation models adopted. This test was performed for the engines equipped with different turbochargers under various operating conditions. The results of calculation showed good agreements with the experimental data and proved that the simulation program developed can be used for the matching of the turbocharger to the engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.3
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• pp.299-306
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• 2015

Turbocharged gasoline direct injection engine is one of promising technologies in the automotive industry. However, reduction in turbo-lag under transient operation is one of important challenging points to improve drivability. Engine transient performance was investigated in a 4-cylinder 2.0 L turbo-gasoline direct injection (T-GDI) engine using Inconel and TiAl (Titanium Aluminide alloy) turbine wheel turbochargers. The TiAl turbocharger performed superior transient boost pressure and torque rises under various engine transient operation conditions. These were mainly due to lower turbine rotational inertia of TiAl turbocharger. The Maximum boost pressure and torque build up were founded in 1500 rpm and 2000 rpm, instant load change from 20% to 100% of pedal position.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.137-142
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• 2016

Variable Geometry System (VGS) is widely applied to the nozzle vane for the radial inflow turbine constituting automotive turbochargers for the purpose of optimizing the power output at each operating condition. In order to improve the performance of radial turbines with VGS, it is necessary to clarify the influences of the setting angle of nozzle vane on the internal flow of radial turbine. However, the experimental measurements are considered to be difficult for the flow in radial turbines because of the small size and the high rotational speed. In the present study, the numerical calculations were carried out for the flow in the radial turbine at three operating conditions by applying the corresponding nozzle vane exit angles, which were set up in the experimental study, as the inlet boundary condition. The numerical results revealed the characteristic flow behaviors at each operating condition.

• Tribology and Lubricants
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• v.34 no.1
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• pp.33-41
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• 2018

This paper describes a new test rig for identification of rotordynamic force coefficients of squeeze film dampers (SFDs) in automotive turbochargers (TCs). Prior studies have mainly concentrated on relatively large-sized SFDs used in aircraft engines, turbocompressors, and turbopumps. The main objective of the current study is to propose a test rig for identification of dynamic force coefficients of small-sized SFDs (a journal diameter of ~11 mm). The current test rig consists of a journal, a SFD cartridge, four support rods, an upper structure, a data acquisition (DAQ) system, and an oil circulation unit. The annular gaps between the journal outer surface and SFD cartridge inner surface create SFD film lands. The damper has two parallel film lands separated by a central groove, having an axial length and depth of 3 mm. Each film land has a length of 4 mm with a $40{\mu}m$ radial clearance. The static load and dynamic impact tests identify the structural characteristics (i.e., stiffness and natural frequency) of the journal and assembled test rig. The measurements show good agreement with predictions. The SFD performance data from this test rig will be used to develop innovative TC rotor systems with improved NVH and reliability characteristics incorporating advanced SFD technology.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.687-692
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• 2016

When turbochargers are applied to engines, the temperature of the engine becomes high, making the cooling of pistons very important. To solve this problem, an oil jet is used. The oil jet provides oil to the underside of piston for cooling. When an oil jet is used, oil pump size-up and oil cooler are needed because of the increased oil flow rate and higher oil temperature. On the other hand, these increase the friction torque of the engine. This study examined how much the friction torque of an engine increases by an oil jet, oil cooler, and oil pump size-up. In addition, the proportions of the friction torque of the engine increased by each part were measured by changing the engine assembly condition. At low speed, the oil pump and oil cooler had a larger effect on the friction torque than the other factors. At high speed, oil cooler had a larger effect than the other factors.